1. Field of the Invention
The present invention relates to a fundus observation device, for observing the state of the fundus oculi of an eye.
2. Description of the Related Art
As a fundus observation device, conventionally a fundus camera has been widely used. FIG. 13 shows one example of the appearance of a conventional fundus camera in general, and FIG. 14 shows one example of an optical system composition to be internally accommodated therein (e.g. JP Patent laid-open No. 2004-350849). Furthermore, “observation” is intended to include at least a case in which produced fundus images are observed (fundus observations with the naked eye may be included).
First, referring to FIG. 13, an explanation is made regarding the appearance of a conventional fundus camera 1000. This fundus camera 1000 is provided with a platform 3 mounted on a base 2 slidably in the front and rear, right and left (horizontal direction) directions. On this platform 3, an operation panel 3a and a control lever 4 are installed for an examiner to conduct various operations.
The examiner may place the platform 3 on the base 2 to be moved 3-dimensionally by operating the control lever 4. On the top of the control lever 4, an operation button 4a is installed to be pressed down to obtain fundus oculi images.
On the base 2, a post 5 is installed standing upwards. On the post 5, a jaw rest 6 where the jaw of a patient is to be rested and an external fixation lamp 7 as a light source for fixing an eye E are provided.
On the platform 3, a main body part 8 is installed to accommodate various optical systems or control systems of the fundus camera 1000. Furthermore, the control system may be installed inside the base 2 or the platform 3, etc., or in an external device such as a computer, etc. connected to the fundus camera 1000.
On the side of the eye E of the main body part 8 (the left side of the page in FIG. 13), an objective lens part 8a disposed opposite the eye E is installed. Also, on the examiner's side of the main body part 8 (the right side of the page in FIG. 13), an objective lens part 8b for observing the fundus oculi of the eye E with the naked is installed.
Furthermore, connected to the main body part 8 is a still camera 9 for producing a still image of a fundus oculi of the eye E and an imaging device 10 such as a TV camera, etc. for producing still images or moving images of a fundus oculi. The still camera 9 and the imaging device 10 are formed removably with respect to the main body part 8.
As a still camera 9, in accordance with various conditions such as the purpose of an examination or the saving method of produced images, etc., a digital camera equipped with imaging elements such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), a film camera, and an instant camera, etc. may interchangeably be used when it is appropriate. The main body part 8 is equipped with a mounting part 8c for interchangeably mounting such a still camera 9.
If the still camera 9 or the imaging device 10 is for taking digital images, the image data of the produced fundus image may be sent to a device such as a computer, etc. connected to the fundus camera 1000 and be observed as a fundus image by being displayed on the display. Also, the image data can be sent to an image storing device connected to the fundus camera 1000 to compile a database and be used as electronic data for creating medical charts, etc.
Furthermore, on the examiner's side of the main body part 8, a touch panel monitor 11 is installed. On this touch panel monitor 11, fundus images of the eye E created based on the video signals output from the still camera 9 (a digital method thereof) or the imaging device 10 are displayed. Moreover, on the touch panel monitor 11, the xy coordinate system with the center of the screen as the origin is displayed overlapped with a fundus image. When the screen is touched by the examiner, the coordinate value corresponding to the touched position is displayed.
Next, referring to FIG. 14, a composition of an optical system of the fundus camera 1000 is described. The fundus camera 1000 is provided with an illuminating optical system 100 to light the fundus oculi Ef of an eye E, an imaging optical system 120 to guide the fundus reflection light of the illumination light to the eyepiece part 8b, a still camera 9, and an imaging device 10.
The illuminating optical system 100 comprises: an observation light source 101, a condenser lens 102, an imaging light source 103, a condenser lens 104, an exciter filter 105 and 106, a ring transparent plate 107, a mirror 108, a liquid crystal display (LCD) 109, an alignment member 110, a relay lens 111, an aperture mirror 112, and an objective lens 113.
The observation light source 101 consists of a halogen lamp, etc. and emits continuous light for observing the fundus. The condenser lens 102 is an optical element that converges the continuous light (observation illumination light) emitted by the observation light source 101 and substantially evenly irradiates the observation illumination light to the fundus oculi.
The imaging light source 103 consists of a xenon lamp, etc. to be flashed when producing fundus oculi Ef images. The condenser lens 104 is an optical element that converges the flash light (imaging illumination light) emitted by the imaging light source 103 and irradiates the fundus oculi Ef evenly with the imaging illumination light.
The exciter filters 105 and 106 are the filters to be used when fluorography of images of a fundus oculi Ef takes a place. The exciter filters 105 and 106 respectively can be inserted and retracted on the optical path by a drive mechanism such as a solenoid, etc. The exciter filter 105 is disposed on the optical path in the event of FAG (fluorescein angiography). Whereas, the exciter filter 106 is disposed on the optical path in the event of ICG (indocyanine green angiography). Furthermore, when color images are being obtained, both exciter filters 105 and 106 are retracted from the optical path.
The ring transparent plate 107 is disposed in a conjugating location with a pupil of the eye E, and is equipped with a ring transparent part 107a taking an optical axis of the illuminating optical system 100 as a center. The mirror 108 reflects the illumination light emitted by the observation light source 101 or by the imaging light source 103 in the direction of the optical axis of the imaging optical system 120. The LCD 109 displays a fixation target (not illustrated) for fixing the eye E.
An alignment member 110 is detachably built into the optical path of an illuminating optical system 100 manually. A first alignment optical system 110A having an optical path perpendicular to the optical path of the illuminating optical system 100 is built into the insert position of this alignment member 110. This first alignment optical system 110A is an optical system for projecting a split indicator used for the diopter scale (focus) adjustment for the fundus oculi Ef onto an eye (e.g., see JP Patent laid-open No. Hei 5-95906).
One example of the configuration of the first alignment optical system 110A is shown in FIG. 15. FIG. 15A is a side view of the first alignment optical system 110A, FIG. 15B is a side view of the alignment member 110, and FIG. 15C is a top view of the alignment member 110.
The alignment member 110 has an inclined surface 110s at the end on the side to be inserted into the optical path of the illuminating optical system 100 as shown in FIGS. 15B and C. This inclined surface 110s acts as a reflection mirror for reflecting light from the first alignment optical system 110A.
The first alignment optical system 110A comprises a light source 110a, a slit 110b, a collective lens 110c, a split prism 110d, a reflection mirror 110e, and a collective lens 110f as well as this alignment member 110 as shown in FIG. 15(A). The light source 110a may, for example, be a light-emitting diode (LED) for emitting light such as a near-infrared light (first alignment light). For example, a rectangle-shaped opening (slit) may be formed on the slit 110b. 
The first alignment light emitted from the light source 110a passes through the opening of the slit 110b, is collected by the collective lens 110c, and is then injected into the split prism 110d. The split prism 110d splits this first alignment light into two light fluxes. The first alignment light having been split into two is respectively reflected by the reflection mirror 110c and focused on the inclined surface 110s of the alignment member 110 by the collective lens 110f. Then, the first alignment light is reflected by the inclined surface 110s, combined with the optical path of the illuminating optical system 100, and injected into the eye E via a relay lens 111, an aperture mirror 112, and an objective lens 113. These two first alignment lights are designed to coincide with each other on the focus surface.
The first alignment light injected into the eye E is reflected by the fundus oculi Ef, received at the image pick up element 10a via the imaging optical system 120, and then displayed on a touch panel monitor 11 (or an external display). The displaying feature of this first alignment light is shown in FIG. 17.
The symbol 110′ in FIG. 17 indicates the shadow of an alignment member 110. In addition, the symbols L1 and L2 in FIG. 17 indicate bright lines which are based on the first alignment light reflected by the inclined surface 110s of the alignment member 110 (alignment bright lines). This pair of alignment bright lines L1 and L2 configures the split indicator described above.
When the fundus oculi Ef does not coincide with the focus surface, the alignment bright lines L1 and L2 are displayed with misaligned each other, i.e. they are misaligned laterally on the paper as shown in FIG. 17A. On the other hand, when the fundus oculi Ef coincides with the focus surface, the alignment bright lines L1 and L2 are displayed in the state in which the crosswise positions coincide with each other as shown in FIG. 17B. An examiner adjusts the focus such that the crosswise positions of the alignment bright lines L1 and L2 coincide with each other.
The aperture mirror 112 is an optical element to combine an optical axis of the illuminating optical system 100 and an optical axis of the imaging optical system 120. In the center region of the aperture mirror 112 an aperture part 112a is opened. The light axis of the illuminating optical system 100 and the light axis of the imaging optical system 120 arc to be crossed at a substantially central location of this aperture part 112a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.
The illuminating optical system 100 having such a composition illuminates a fundus oculi Ef in the following manner. First, the observation illumination light is emitted when the observation light source 101 is lit during fundus observation. This observation illumination light irradiates the ring transparent plate 107 through the condenser lenses 102 and 104. (The exciter filters 105 and 106 are retracted from the optical path.) The light passed through the ring transparent part 107a of the ring transparent plate 107 is reflected by the mirror 108 and is reflected along the optical axial direction of the imaging optical system 120 due to the aperture mirror 112 through the LCD 109 and the relay lens 111. The alignment member 110 has been manually retracted from the optical path in advance. The observing illumination light reflected by the aperture mirror 112 advances in the optical axial direction of the imaging optical system 120 and is converged by the objective lens 113, to be made incident onto the eye E, and illuminates the fundus oculi Ef.
Then, the ring transparent plate 107 is disposed in a conjugating location with the pupil of the eye E, and on the pupil a ring shaped image of the entering observation illumination light is formed. The fundus reflection light of the entered observation illumination light is to be emitted from the eye E through a central dark part of the ring image on the pupil. As described, it is to protect the effect of observing illumination light entering the eye E with respect to the fundus reflection light of the observing illumination light.
On the other hand, when imaging the fundus oculi Ef, flush light is emitted from the imaging light source 103 and the imaging illumination light is irradiated onto the fundus oculi Ef through the same path. In the event of photofluographing, either the exciter filter 105 or the exciter filter 106 is disposed selectively on the optical path depending on whether FAG imaging or ICG imaging is carried out. Furthermore, when imaging the fundus oculi Ef other than photofluography, or when observing the fundus oculi Ef, the exciter filter 105 and 106 are retracted from the optical path.
Whereas, imaging optical system 120 comprises: an objective lens 113, an aperture mirror 112 (an aperture part 112a thereof), an imaging diaphragm 121, a barrier filter 122 and 123, a focusing lens 124, half mirror 190, a relay lens 125, an imaging lens 126, a quick return mirror 127 and an imaging media 9a. Herein, the imaging media 9a is an arbitrary imaging media (image pick-up elements such as CCD, camera film, instant film, etc.) used for a still camera 9.
The fundus reflection light of the illumination light, emitted through the central dark part of the ring shaped image formed on the pupil from the eye E, enters the imaging diaphragm 121 through the aperture part 112a of the aperture mirror 112. The aperture mirror 112 reflects cornea reflection light of the illumination light and acts so as not to mix the cornea reflection light into the fundus reflection light made incident onto the imaging diaphragm 121. As a result, the generation of flare on the observation images and/or produced images is prevented.
The imaging diaphragm 121 is a plate shaped member at which plural circular light transparent parts of different sizes are formed. The plural light transparent parts constitute different diaphragms with different diaphragm values (F value), and are to be disposed alternatively on the optical path by a drive mechanism (not illustrated herein).
The barrier filters 122 and 123 can be inserted and retracted on the optical path by a drive mechanism such as a solenoid, etc. In the event of FAG imaging, the barrier filter 122 is disposed on the optical path while in the event of ICG imaging the barrier filter 123 is inserted onto the optical path. Furthermore, when imaging the fundus oculi Ef other than photofluography, or when observing the fundus oculi Ef, the barrier filters 122 and 123 are to be retracted from the optical path.
The focusing lens 124 is enabled to move in the light axial direction of the imaging optical system 120 by a drive mechanism (not illustrated herein). This movement of the focusing lens 124 allows to change the magnifying ratio in observation and the magnifying ratio in imaging, and to focus images of a fundus oculi (focus adjustment). The imaging lens 126 is a lens to focus the fundus reflection light from an eye E on the imaging media 9a. 
The quick return mirror 127 is disposed rotatably around a rotary shaft 127a by a drive mechanism not illustrated herein. In the event of imaging a fundus oculi Ef with the still camera 9, the fundus reflection light is supposed to be guided to the imaging media 9a by springing up the quick return mirror 127 that is obliquely mounted on the optical path. Whereas, in the event of imaging a fundus oculi with an imaging device 10 or of observing the fundus oculi with the naked eye of the examiner, the quick return mirror 127 is to be obliquely mounted on the optical path to upwardly reflect the fundus reflection light.
The imaging optical system 120 is further provided, for guiding the fundus reflection light reflected by the quick return mirror 127, with a field lens 128, a switching mirror 129, an eyepiece 130, a relay lens 131, a reflection mirror 132, an imaging lens 133 and an image pick up element 10a. The image pick up element 10a is an image pick up element such as CCD, etc. installed internally in the imaging device 10. On the touch panel monitor 11 a fundus oculi image Ef′ imaged by the image pick up element 10a is be displayed.
The switching mirror 129 is to be rotatable around the rotary shaft 129a as well as the quick return mirror 127. This switching mirror 129 is obliquely disposed on the optical path during observation with the naked eye and guides reflected light on the fundus oculi to the eyepiece 130.
Also, when a fundus image is formed by the imaging device 10, the switching mirror 129 is retracted from the optical path, and the fundus reflection light is guided toward an image pick-up element 10a. In this case, the fundus reflection light is directed toward a relay lens 131, is reflected by the mirror 132, and is focused on the image pick-up element 10a by the imaging lens 133.
A half mirror 190 is provided on the optical path between the focusing lens 124 and the relay lens 125 while the half mirror 190 is inclined. This half mirror 190 acts to combine the path of the second alignment optical system 190A shown in FIG. 16A with the path of the imaging optical system 120 (photographing optical path). This second alignment optical system 190A is an optical system for projecting a bright point (alignment bright point) used for the position adjustment (particularly adjustment of the working distance) of an optical system in relation to an eye E onto an eye E (e.g., see JP Patent laid-open No. Hei11-4808).
The second alignment optical system 190A comprises a light source 190a consisting of, for example, LED for emitting light such as a near-infrared light (second alignment light), a light guide 190b, a reflection mirror 190c, a two-hole aperture 190d, and a relay lens 190e as well as the half mirror 190.
The two-hole aperture 190d has two holes 190d1 and 190d2 as shown in FIG. 16B. The holes 190d1 and 190d2 are formed on, for example, the symmetric position for the center position 190d3 of the circular two-hole aperture 190d. The two-hole aperture 190d is arranged so that this center position 190d3 is located on the optical axis of the second alignment optical system 190A.
The second alignment light ejected from an ejection end 190β of the light guide 190b is reflected by the reflection mirror 190c and guided to the holes 190d1 and d2 of the two-hole aperture 190d respectively. The alignment lights that have passed the hole 190d1 and 190d2 are guided to the aperture mirror 112 by passing through the relay lens 190e and by being reflected by the half mirror 190. Then, the relay lens 190e focuses the image of the ejection end 190β of the light guide 190b on the center position of the hole 112a of the aperture mirror 112 (the position on the optical axis of the imaging optical system 120). The second alignment light that has passed through the hole 112a of the aperture mirror 112 is projected onto the cornea of the eye E via objective lens 113.
Herein, suppose that the positional relationship between the eye E and a fundus oculi camera 1000 (objective lens 113) is appropriate, i.e. that the distance from the eye E to the fundus oculi camera 1000 (working distance) is appropriate, and that the optical axis of the optical system of the fundus oculi camera 1000 and the eye axis of the eye E (top position of the cornea) are (almost) coincident with each other. In this case, two light fluxes (alignment light fluxes) formed by the two-hole aperture 190d are projected onto the eye E so as to be focused on the intermediate position between the top of the cornea and the center of corneal curvature. Meanwhile, when the working distance W from the eye E to the device main body is not appropriate, two alignment light fluxes will be separately projected onto the eye E, respectively.
The corneal reflection lights of the two alignment light fluxes (the second alignment light) are received by the image pick up element 10a via the imaging optical system 120. The photographed images by the image pick up element 10a are displayed on the touch panel monitor 11 (or an external display). The displaying feature of this second alignment light is shown in FIG. 17.
The symbol S in FIG. 17 indicates the scale having bracket shape, and symbols P1 and P2 indicate the light received image of two alignment light fluxes (alignment bright points). The scale S is displayed on the touch panel monitor 11 so that its center position coincides with the optical axis of the imaging optical system 120.
When the positional relationship between the eye E and the fundus oculi camera 1000 is not appropriate, the alignment bright points P1 and P2 are displayed in the state of being separated from each other as shown in FIG. 17A. Particularly, when the positions of the eye E and the fundus oculi camera 1000 are out of alignment together in the up-and-down direction or the right-and-left direction, the alignment bright points P1 and P2 are displayed at the position, in which they are out of alignment to the scale S in the up-and-down direction or the right-and-left direction.
On the other hand, when the positional relationship between the eye E and the fundus oculi camera 1000 is appropriate, the alignment bright points P1 and P2 are displayed in the scale S in the state of being overlapped with each other as shown in FIG. 17B. An examiner adjusts the positional relationship between the eye E and the fundus oculi camera 1000 such that the alignment bright points P1 and P2 overlap each other and are displayed on the scale S.
Such a fundus camera 1000 is a fundus observation device to be used for observing the state of the surface of a fundus oculi Ef, that is, the retina. In other words, a fundus camera 1000 is a fundus observation device to obtain a 2-dimensional fundus oculi image when it sees the fundus oculi Ef from the corneal direction onto the eye E. On the other hand, in the deep layer of retina tissues such as the choroidea or sclera exist, technology for observing these deep layer tissues has been desired, but, in recent years, devices for observing these deep layer tissues have been practically implemented (e.g. JP Patent laid-open No. 2003-000543, JP Patent laid-open No. 2005-241464).
The fundus observation device disclosed in JP Patent laid-open No. 2003-000543 and JP Patent laid-open No. 2005-241464 are devices to which so called OCT (Optical Coherence Tomography) technology is applied. With such fundus observation devices, low coherence light is split into two, one of which (signal light) is guided to a fundus oculi and the other one (reference light) is guided to a given reference object, and this is a device to form tomographic images of the surface and the deep layer tissue of a fundus oculi,and to form the 3-dimensional image from the tomographic images, by detecting and analyzing the interference light obtained by overlaying the signal light that has reached the fundus oculi and the reference light that has been reflected by the reference object. Such devices are in general called a Fourier domain OCT.
For such an optical image measuring device, the focus and position of the optical image measuring device in relation to the eye should be adjusted by using alignment indicators such as the same alignment bright line and alignment bright point as the fundus oculi camera 1000 described above.
In addition, the present inventors proposed a fundus observation device capable of capturing both images of the surface and tomographic images of the fundus oculi (e.g., see JP Patent Application No. 2006-003065 and JP Patent Application No. 2006-003878), but there was a disadvantage in that when an alignment indicator is projected onto the eye during capturing images of the surface of the fundus oculi, the image of the projected region cannot be observed. Particularly, as a configuration described in Patent Application No. 2006-003878, in the case of using an image of the surface of the fundus oculi to correct the position of a tomographic image, and when using an image of the surface of the fundus oculi into which an alignment indicator is reflected, correction may not be accomplished adequately.
The present invention is designed to solve such disadvantages and therefore is intended to provide a fundus observation device capable of capturing both images of the surface of the fundus oculi and tomographic images of the fundus oculi, and capable of preventing alignment indicators from being reflected in the image of the fundus oculi.
Particularly, the present invention is intended to provide technology that prevents alignment indicators from being reflected into the image of the surface of the fundus oculi, while the image is used for correcting the position of tomographic images of the fundus oculi.